The invention relates to an air spring having an elastomeric air spring flexible member having respective ends which are tightly attached to respective attachment components. The air spring flexible member forms an air spring volume which is closed off and can be charged with pressure. Each of the ends of the flexible member has a conical or clampable sealing bead.
Air springs having a flexible member of elastomeric material have been proved for decades as load controllable spring elements in the area of vehicle manufacture and in industrial areas. The air spring flexible member is sealed off at the two open ends by means of attachment components and is attached via these attachment components, for example, to road motor vehicles between chassis and axle.
Basically, one distinguishes the air spring flexible members as rolling-lobe flexible members and as folding flexible members. In rolling-lobe flexible members, one of the two attachment components is configured as a so-called roll-off piston on which the rolling lobe of the rolling-lobe flexible member can run.
Various sealing connecting types are known in order to obtain a tight seat of the ends of the air spring flexible member on the attachment components. The flexible member ends have either sealing beads with conical sealing surfaces or are attached via clampable sealing beads to the attachment components. For rolling-lobe flexible members, the flexible member end, which lies opposite the rolling lobe, is often provided with a clampable sealing bead which is connected to the bent-over plate defining the attachment component; whereas, the end of the flexible member, which seats tightly on the roll-off piston, is configured as a conical seal seat.
Air spring flexible members having clampable sealing beads are either screw connected tightly to an attachment component configured as a bent-over plate or screw connected to the attachment component by means of a peripherally extending attachment part. By bending over the edge of the plate around the clampable sealing bead, a form-tight and sealing connection is provided between the two parts.
The seal tightness of the form-tight connection between the flexible member end and the attachment component is not always satisfactory over a long period of time. Fluctuations in material and tolerances of the components can prevent the manufacture of a uniform clamping gap when bending over the edge of the attachment plate. The rubber layer which defines the sealing surface in the clamping gap is often so thin that gap nonuniformities cannot always be reliably compensated. In the worst case, leaks can occur and these require considerable supplemental work.
It is an object of the invention to provide an air spring of the kind described above wherein a reliable and more secure seal is made possible between the respective ends of the flexible member and the attachment components.
The air spring of the invention includes: a first attachment component; a second attachment component; an annular flexible member made of elastomeric -material and having first and second end portions tightly attached to the first and second attachment components, respectively; the end portions having respective sealing beads defining respective seals with the attachment components; the flexible member and the attachment components conjointly defining a closed off air spring volume which can be charged with pressurized air; at least one of the attachment components having an inner wall surface facing toward and delimiting the closed off air spring volume; the flexible member having an end face at at least one of the end portions; an elastic peripherally extending sealing projection formed on at least the one end portion so as to project away from the end face and so as to define a smallest diameter of the flexible member; the sealing projection being configured to face directly toward the air spring volume so as to be subjected to the charge of pressurized air; and, the sealing projection having an inherent stress causing the sealing projection to lie in sealing contact engagement against the inner wall surface of the one attachment component corresponding to the one end portion.
The peripherally extending sealing lip is on the inner periphery of at least one of the ends of the flexible member. The sealing lip projects beyond the end face of the flexible member so that the sealing lip swings away laterally in the direction of the end face plane when pressed against the seal seat or the attachment component because of the elastic configuration and presses against the attachment component because of its inherent stress opposing this swing direction. In this way, a sealing action is obtained directly to the pressure chamber, that is, the air spring volume. This sealing lip arrangement lies forward of the main seat where the sealing bead is clamped and has only the function of sealing. The holding function is performed by the sealing bead so that a reliable separation of the two functions is ensured.
According to a feature of the invention, the sealing lip is configured so as to have a rectangular shape. This embodiment is characterized by an excellent forming and has an enlarged elastic portion against the sealing surface.
According to another embodiment of the invention, the sealing lip is tapered toward its end and is configured to be inclined toward the interior of the flexible member. This sealing lip lies snugly against the attachment component.
In still another embodiment of the invention, the sealing lip is provided with a slit and, according to still another embodiment, the sealing lip can be configured so as to be half round. These configurations can form themselves especially well and have an increased elastic portion against the sealing surface.